Machine for grinding parallel surfaces



Nov. 25, 1958 7 Sheets-Sheet 1 Filed Nov. 28, 1955 a H @w m .M\ 0 \x mfiw L Nov. 25, 1958 Filed Nov. 28, 1955 R. G. ELLIS 2,861,400

MACHINE FOR GRINDING PARALLEL SURFACES 7 Sheets-Sheet 2 INVENTOR. F0 770&= 1/27 s.

Nov. 25, 1958 R. G. ELLIS,

MACHINE FOR GRINDING PARALLEL SURFACES 7 Sheets-Sheet 3 Filed Nov. 28,1955 INVENTOR.

F0770 IZ/zlsc M J1 TOWNEV-$ NOV. 25, 1958 ELLIS 2,861,400

MACHINE FOR GRINDING PARALLEL SURFACES Filed Nov. 28, 1955 7Sheets-Sheet 4 INVENTOR. E .4=. F0770 d Z'Z'Zzls'.

Nov. 25,- 1958 R. G. ELLIS MACHINE FOR GRINDING PARALLEL SURFACES 7Sheets-Sheet 5 Filed Nov. 28, 1955 INVENTOR. 5 [7778.

*Bha fay/2504s? Nov. 25, 1958 R. G. ELLIS 2,861,400

MACHINE FOR GRINDING PARALLEL SURFACES Filed Nov. 28, 1955 '7Sheets-Sheet 6 INVENTOR. 307% & ZIZZzLs.

Nov. 25, 1958 R. G. ELLIS 2,851,400

MACHINE FOR GRINDING PARALLEL SURFACES Filed Nov. 28, 1955 7Sheets-Sheet 7 INVENT R. I] z i Em: v.

FNZ/ST United States '7 Rollo G. Ellis, Royal Oak, MiClL, assignor toMicromatic Hone Corporation, Detroit, Mich, a corporation of MichiganApplication November 28, 1955, Serial No. 549,427

18 Claims. (Cl. 51-118) This invention relates to improved flat surfacelappers and more particularly to flat surface lappers of the opposedwheel type for grinding opposed faces on workpieces.

In contemporary abrading and lapping machines, as the condition of thewheels or laps deteriorate due to wear, they do so irregularly,resulting in poor quality of output. Uniformity of workpiece size andmaintenance of parallelism between the opposed faces of the workpiecehave heretofore been exceedingly difficult to achieve in a singleoperation. It is typical of present-day lappers to have a highpercentage of rejects since it is not uncommon for workpieces to bepermanently ruined due to their being machined undersize or with theiropposed faces nonparallel.

This nonuniform wear, which has been characteristic of conventionallapping machines, lowers production efficiency in that frequentinterruption is required for supplemental dressing of the abradingwheels. Frequent shut-downs for supplemental dressing of the abradingwheels are costly as they greatly reduce the production throughput ofthe machine. Moreover, with each supplemental dressing, the ratherexpensive abrading wheels are deeply cut by the diamond dressers, thussacrificing a good deal of the working surfaces of the abrading wheels.

With the foregoing in view, it is an important object of the presentinvention to provide a fiat surface lapper which is economical inoperation and wherein the production efliciency of the same is greatlyenhanced.

It is another object of the present invention to provide a flat surfacelapper wherein uniformity of work size and parallelism between opposedfaces of workpieces are consistently maintained.

It is another object of the present invention to provide a flat surfacelapper which automatically compensates itself for the condition of itsabrading wheels to maintain a predetermined gap therebetween.

It is another object of the present invention to provide a fiat surfacelapper which is responsive to the precision quality of its output andwhich exercisesa control over the condition affecting said quality.

It is another object of the present invention to provide a fiat surfacelapper wherein workpieces are fed between the abrading disks in a novelmanner so as to produce a characteristic wheel wear which maintainsparallelism between the abrading disks throughout the life of the same.

It is another object of the present invention to provide a fiat surfacelapper wherein workpieces are fed between the abrading disks in a novelmanner so as to establish annular zones of abrasion between the workingsurfaces of the abrading wheels.

It is another object of the present invention to provide 7 *atentabrading wheels which alternate in the type of work burden said annularzones assume.

It is another object of the present invention to provide a flat surfacelapper wherein workpieces are fed between the abrading disks in a novelmanner so as to uniformly distribute the abrading effort over the entireworking surfaces of the abrading wheels, virtually eliminating the needfor supplemental dressing. 7

Other objects and advantages of the present invention will be apparentduring the course of the following description, taken in conjunctionwith the accompanying drawings, forming a part of the specification, andin which like numerals are employed to designate like parts throughoutthe same:

Figure 1 is a plan view of the machine of the present invention;

Fig. 2 is a right side elevation of the machine shown in Fig. 1;

Fig. 3 is a front elevation of the machine of Fig. 1;

Fig. 4 is a vertical section taken along the line 4-4 of j Fig. 1 withthe feed disk swung out of. position;

Fig. 5 is a fragmentary left side elevation of the machine shown in Fig.3 with certain parts removed for the purposes of clarity; v V

Fig. 6 is a sectional view taken along the line 6 -6 of Fig. 5; a

Fig. 7 is a view taken along the line 7-7 of Fig. 1,

partly in section;

Fig. 8 is an enlarged plan view showing in detail certain portions ofthe machine shown in Fig. 1;

Fig. 9 is an elevation partly in section of certain parts of Fig. 8viewed as shown by the line 99 of Fig.- 8; Fig. 10 is a vertical sectiontaken along the line 10-10 of Fig. 8; and 7 Fig. 11 is an elevation ofcertain parts of Fig. 8 viewe as shown by the lines 1111 of Fig. 8.

Referring now to the drawings, wherein for the purpose manner forreasons which will appear more fully herein-' after. Disposed above feeddisk 17 is a feed chute, designated generally at 21, which conveysworkpieces 23 into the workpiece-receiving apertures 19 on feed disk 17.

After the workpieces 23 are placed in the workpiece receiving apertures19 on the feed disk 17, they are conveyed in the direction of the arrowinto the working gap 25 (Fig. 4) between an upper abrading disk 27 and alower abrading disk 29. In passing between the upper abrading disk 27and the lower abrading disk 29, the workpieces 23 have their opposedfaces ground to a predetermined size between their time of entry intoand exit from the working gap 25. Upon their exit from the working gap.they pass between a sensing means, for example, a thickness gauge 31,whose function will be hereinafter more particularly described. Thoseworkpieces which meet the standards predeterminedly set for the machineare dropped to a con-v veyor belt 33 disposed beneath the feed disk 17whereby they are conveyed to a handling or take-.offstation. Those awhich are too thick to meet the predetermined standards are required'torepeat their passage through the Working gap for additional stockremoval;

Patented Nov. 25, 1958 Rotary motion of abrading disks The abradingdisks 27 and are driven in the same direction of rotary movement asthatof feed disk 17. Their motion is continuous, but their relativespeeds difier slightly so as to permit a, gradual and continual changeof orientation between the upper and lower work surfaces of the abradingdisks. The drive for the abrading disks is a motor 35. The motr'35,through V-belts and pulleys, drives-a shaft 37 which is the common driveshaft for rotating the upper and lower abrading disks. The lowerabradingdisk 29 is rotated from the shaft 37 by thematingofa worm screw 39secured to the shaft 37 with a worm gear'41, The worm gear 41 is securedto a base member 3 upon which, is affixed a backing plate 55 for thelowerabrading disk 29.. vThehase member 53 is rotatably carried on athrust ring;57z and a stationary thrust -s eat;59 The assembly. Of thelower abrading disk 29 and the base member 53 are adapted to rotateabout a stationary cente post 651 bymeans of bearing sleeves 61 and 63.

Also driven from the shaft 37 by a belt 43 and a pulley 45 (Fig. 3 is ashaft 47 which rotates the upper abrading wheel 27 through a worm screw49, and a worm gear 51 (Fig 4). The upper abrading disk 27 is carried byashaft 67 through a flange assembly 69 at its upper end, which, in turn,is secured to a backing-plate 71. The

shaft 67'issplined at its lower endso that it may assume differentvertical positions and still be rotated by the worm-gear 51.

Vertical motion of the abradinig wheels Relatively speedy adjustment ina vertical direction of the upper abrading-disk 27 'i sprovided by apiniongear 73 which mates with a toothed segment 75 of an outercylindrical spindle 77 disposed aboututhe shaft 67 for moving the samein a vertical direction. Motion is-imparted to the'pinion gear 7,3,through :arack 79 which moves backward and forwardjinahorizontaldirection. Therack 79 is connected to a piston rod 81 of'a fluidactuatedcylinder 83 aflixed onanyupfight side of the machinebaselia.Backwardandforward motion of the rack 79 causes the pinion 73 to rotateonits axis and raise or lower the cylindrical spindle 77 a and its upperabrading disk 27 in response to the movement of the PiStQnrod 81 of thefluid-actuated cylinder 83. This provides relatively fast movement ofthe upper abrading disk 27 toward'or away from thelower abrading disk29, for various-purposes, for example, for replacing the abrading disks,for setup to accommodate workpieces of differentsize for a newoperationand for initial dressing. Provision is also made for lineadjustment of the gap between the abrading wheels. This maybe donemanually if; desired, although it is a special feature of the presentinvention to provide for automatic adjustment of the gap between theabrading wheels to compensate for continual wear of the same during use.To accomplish this fine adjustmentof the gap between the abradingwheels, there are'arranged rollers 85 at the lower extremity of thecylindrical member 77. The rollers 35 ride on a wedge 87 whichconstitutes anadjustable dimensional stop for regulating the gapbetweentheworking surfaces of the abrading wheels. Figs. 5 and 6 showinmore detail how the actuation of the wedge 87 is accomplished. Thewedge 87 is supportedfrom below by the rollers 89 and. may be actuatedlaterally in increments by a screw 91 which is threadably engaged withthewedge 87. The screw 91 maybe manually rotated by a handwheel 93 soasto either raise or lower the upper abrading disk' de pending upon thedirection in which the handwheel 931s rotated. g I

Automatic actuating means are'also provided for lateral adjustment ofthe wedge 87; This consists'of a gear 7 motor 95 which rotatably drivesa pinion 97 which, in turn, meshes with a gear 99 causing the latter torotate continually so long as the motor 95 is in operation. A gear 101,however, which meshes with a gear 103, the latter ultimately turning thescrew 91, does not rotate together with the gear 99 except when amagnetic clutch 165 is energized. The operation of the magnetic clutchis controlled by an electrical switch 107 (Fig. 5). The switch 107, inturn, is opened and closed by a cam 109 mounted on the shaft of the gearmotor 95. The cam 109 is provided with an adjustable lobe 111 whichperiodically releases a follower roll 113' to close the switch 167.While the follower roll 113 of the switch 107 is released by the lobe111 of the cam 109 during each revolution of the cam, the magneticclutch is momentarily engaged by conduction of electrical currentthrough collector rings 115, providing that the gap between the abradingwheels requires adjustment for correction of wheel wear. The sensingmeans to determine whether the abrading wheels need vertical adjustmentfor wheel wear will be hereinafter more particularly described, alongwith its relation to the above-described means for fine adjustmentvertically of the gap between the abrading wheels. If no correction isneeded, as determined by the sensing means to be hereinafter described,no current will flow through the collector rings 115 even though theswitch 107 is closed by the lobe 111 on the cam 109. Hence, the magneticclutch will not be engaged unless a correction for wheel wear isrequired.

Intermittent feed motion The feed diskfor introducing the workpiecesbetween the working surfaces of the abrading wheels may be drivencontinuously, although it is preferred that an intermittent feed motionbe employed. Intermittent indexingof the workpieces substantiallyeliminates the need for supplemental dressing of the abrading wheels. Ithas been found that by rapidly moving the workpieces through successivepositions of rest, the abrading wheels initially wear to a state ofstability and thereafter the wear on the abrading wheels becomesuniform. Because the bulk of work by the abrading effort is performedduring stages of rest, wear of the abrading wheels correlates to thedimensional change in the workpieces as they proceed through theoperaing cycle. The abrading wheels will inherently acclimate themselvesto a. steady state in each annular zone of abrasion where a workpiece isbeing ground. With a controlled time of dwell of each workpiece in eachzone of contact, and \vitha rapid transference of the workpieces throughsuccessive zones, the

working surfaces of the abrading wheels adjust to a steady state in eachzone of abrasion which produces a characteristic wheel wear so as tomaintain the working surfaces parallel throughout the life of theabrading disks as will be developed in detail hereinafter. It is theabove type of motion which the term intermittently index, as used in theappended claims, is intended to mean, viz., a progressive advance of theworkpieces wherein they are hesitated in a position of rest andthereafter rapidly transferred to a new position of rest.

Before description of the intermittent feed employed with the device ofthe present invention, a special feature will be noted concerning thenovel means of feeding the workpieces between the working surfaces ofthe abrading wheels. Reference is made to Fig. 1, wherein a number ofannular zones of abrasion established during the machining operation arerepresented by mean radii y, y, y", x, x and x. Although all stations ofthe feed disk lying between the abrading wheels contain a workpiece, notwo of them occupy the same annular zone of abrasion in the smi ing surfes of the bradin wheels. Mean radius y; for example, passes through thecenter of workpiece 23a at the exit side of the feed disk and yet passesthrough the mid-point of the space between the workpieces 23b land 23con the entrance side of the feed disk. Similarly,

mean radius y passes through the center of a workpiece at the exit sideand passes through the mid-point of. the

space between two workpieces on the entrance side, and- By disposing theworkpieces in such array, there are established annular zones ofabrasion in the working surfaces of the abrading wheels, each of whichdoes work on a different workpiece at one time and each of theworkpieces in succession. The annular zones of abrasion in the workingsurfaces of the abrading wheels will acclimate themselves to a steadystate of wear so that the abrading disks are maintained parallel becauseof the amount of work performed in each zone and the disposition of theseveral zones. The centers of the annular zones through the peculiardisposition of the workreceiving apertures in the feed disk will bealternately disposed through the cross-section of the abrading wheels.That is to say, the centers of the annular zones, which containworkpieces on the entrance side of the feed disk, will alternate withthe centers of the annular zones which contain workpieces on the exitside of the feed disk. Since the workpieces on the exit side of the feeddisk are in a slightly greater state of completion than those on theentrance side of the feed disk, the amount of wear in the annular zoneson the exit side of the feed disk will be successively slightly lessthan the amount of wear in the annular zones on the entrance side of thefeed disk. This will result in annular zones of alternately greater andless wear throughout the cross-section of the abrading wheels, thoughthe variations in the amount of wear in each annular zone, of course,will be very small, depending upon how much work is done upon theworkpieces from the time of their entry until the time of their exit.Nonetheless, the disposition of these annular zones of abrasion h inglternately slightly greater and slightly less wear throughout thecross-section of the abrading wheels results in maintenance of superiorparallelism be tween the abrading wheels. This superior parallelismimparted to the abrading wheels by the characteristic wear thereof isthought to account for the unexpected result that the need forsupplemental dressing of the abrading wheels is eliminated. Furthermore,this superior parallelism maintained in the abrading wheels effects aprecision type of grinding whereby workpieces are produced havingconsistently parallel opposed faces and which are of uniform size.

As has been previously pointed out, the use of an intermittent feedmechanism for the rapid transference of the workpieces throughsuccessive positions of rest causes the abrading wheels initially towear toward a state of stability and uniformly thereafter. Intermittentindexing of the workpieces through the working gap is a substantialfactor among others contributing toward elimination of the need forsupplemental dressing of the abrading disks.

The intermittent feed mechanism will now be described. The firstworkpiece, having been rapidly indexed to position by feed disk 17, isoperated upon by the abrading wheels While the workpiece is statictherebetween. After a sufficient time interval, the workpiece is rapidlyin- 6 dexed to its succeeding position. During each such index, apreceding workpiece is moved into the zone which has been vacated by thesucceeding one. Eventually all of the zones contain a workpiece, each ina slightly more advanced state toward completion than the preceding one.The mechanism for intermittently indexing the feed disk, i. e., causingintermittent movements with relatively long periods of rest between suchmovements is accomplished by well-known means, such as the Genevamovement shown in Fig. 7. A Geneva cam wheel 117 is keyed to a shaft 119on the lower portion of which is secured a pinion gear 121 which mesheswith a gear 123 on the lower end of a feed disk spindle 125. The feeddisk spindle 125 is adapted to rotate about its vertical axis inaccordance with actuation from the Geneva cam wheel 117. The Genevawheel 127, secured to a shaft 128, has a plurality of pin rollers 129secured thereto and as they rotate in succession, they engage with theGeneva cam wheel 117 causing intermittent rotary movement to occur inthe feed disk 17 throughits spindle 125. The Geneva wheel 127 is rotatedthrough a worm gear 131 keyed to the shaft 128 of the Geneva wheel 127meshing with a worm screw 133. The worm screw 133 is secured to a shaft135 and driven through a series of V-belts and pulleys by a motor 137.The Geneva wheel 127 is driven from a variable speed drive so as tocontrol the rate at which the workpieces are indexed through the workinggap. The shaft 128 of the Geneva wheel 127 also drives the conveyor 33to carry away workpieces after ejection from the feed disk to anunloading station. The preferred conveyor shown is a link chain'conveyorand it will be apparent that other elongated conveying means may beemployed.

Vertical adjustment of the indexing mechanism It has been previouslyshown that the upper abrading wheel is automatically adjusted in heightrelative to the lower abrading wheel to compensate for wear of thewheels as the grinding operation proceeds in order to control thethickness of workpieces produced. As the wheels wear, it is expedientthat the indexing disk 17 also be periodically adjusted so as tocontinually maintain approximate midposition between the upper and lowerabrading wheel faces. Vertical adjustment of the indexing mechanism canbe accomplished both manually and automatically. Manual adjustment isaccomplished by turning a handwheel M51 (rigs-2 and 3), although duringoperation, adjustment takes place automatically. Auto matic adjustmentof the indexing mechanism is accomplished through a sensing meansresponsive to a follower riding on the lower abrasive wheel, as will bepresently described. Before this, however, the mechanism for verticalmovement of the indexing assembly will be described. The source of powerfor vertical movement of the indexing assembly comprises a gear motor139 carrying a helical-toothed pinion 141 which, in turn, meshes with agear 143 mounted on an adjusting screw 145. The adjusting screw 145 isdisposed within a vertical post 147 and threadably engages the upperportion of a supporting block 149 for the feed mechanism to verticallymove the same. Depending upon the'direction of rotation of the gearmotor 139, the' feed mechanism will be caused to move upward or downwardon the post 147. Inorder to eliminate undue bending moments on the post147 by the weight of the supporting block 149, additional support isprovided under the center of the shaft 125 for the feed disk, as shownby the support block screw 153. The screw 153 is actuated by ahelicaltoothed shaft 155 meshing with gears 157 and 143. Thus, theadjusting screws 145 in timed relation so as to maintain the feed diskhorizontal regardless of its position of adjustment.

As mentioned, thereis present invention means for automaticallyadjusting the height of the feed disk in order that it will be at all151 carried by a and 153 may be caused to move 2 provided in the deviceof the times. be substantially midway between the abrading wheels.During the grinding .operation the abrading wheels. gradually .wear andcompensation for this wear automatically occurs through the lowering ofthe ,upper abrading wheel relative to the lower abrading wheel inresponse to workpiece oversize. As the gap between the abrading wheelsis adjusted for wheel wear, so also is the height of the feed diskadjusted- Automatic regulation of this adjustment of the feed disk ismade responsive to wheel wear, and the means (as best shown in Figs. ,8,9, 10 and 11) foraccomplishing this regulation will now be described.The means for. automatically adjusting the height of the indexingmechanism as the abrading wheels wear isresponsive to..a.follower roll15.9 riding .on the upper face of thelcwerabrading wheel 29. The followeroll 159. isrotatably disposed in a follower housing 162 mounted on afollower. base 161. Thefollower base 161.

is floatably carried and partially counterbalanced on guide pins 163'and 165through. leg portions 164 and 166 in such a manner as tobesupported in its vertical position by the contact of. the followerroll 159 on the upper surface of lower abrading wheel 29. .The axis .ofrotation of the follower roll 159 is so disposed (asshownin Figs. 9 and10) as to contact only the lower abrading wheel. As the lower abradingwheel 29 wears, the Weight of the follower base161 causes thefollowerroll 159 to follow the wheel wear downward. A depending foot 167 issecured to the follower base .161and moves downward with the followerroll 159 and the follower base 161.

The depending foot 1671s that part of the circular track 176 which runsbeneath the'workpieces from the exit end to the entrance end of theworking gap. The depending foot 167 represents a break in the track 176just before the entrance end of the working gap and serves to retain theworkpieces in the work-receiving apertures 19 in their final path oftravel toward the working gap. 7 The depending foot 167 which movesdownward in response to wheel wearhas a sensitive switch 169 mountedthereon. The sensitive switch 169 in its downward travel with thefollower roll 159 is actuated by a trip arm 171 mounted on the'track 176for the indexing assembly carrying the feed disk 17. The. track 176.ismounted on the support 149 for the indexing mechanism which isadjustable vertically, as previously described, by the gear motor 139(Fig. 7). 169 and the triparm 171 determines whether or not the gearmotor 139 is energized. When it is energized, the entireindexing'assembly ismoved ina vertical direction, the arrangement of'theadjustable supports being such that the feed disk is alwaysmaintained horizontal regardlcss of .the' vertical position to which theindexing mechanism is adjusted. The sensitive switch 169 is caused toapproachthe'triparm.171.in response to a change in vertical positionof:the follower roll 159 resulting from wear on the lowertabradinglwheel29. In due course, when suflicient accumulated change of positionbetween the sensitive switch 169 and the trip arm 171 has occurred,thelcontacts of the sensitive switch 169 will close,

thereby energizing the gear motor 139 which moves the indexing assemblytogether with the feed disk downward. This movementcauses thetrip arm171 to gradually'recede from the sensitive switch 169. When sufficientdownwardmovernent has occurred to open the contacts of the sensitiveswitch 169 by relaxation of its pressure against the trip arm 171, thegear motor 139 is de-energized and the indexing mechanismretains thisnewly adjusted position. This new position of the trip arm 171 is shownin dotted lines in Fig. 11 by the reference numeral 171'. As theabrading wheels continue to wear, in due timethe follower roll 159 willagain move vertically downward together with the follower base 161 andthe depending foot 167.: The depending foot 167 will carry The relativepositions of the sensitive switch L This'new position of .the sensitive.switch 169 is shown in Fig. 11 by the. reference numeral169, Thecontinued downward movement of the follower roll 159 will graduallyincrease the pressure between the trip arm 171' in its new position andthe sensitive switch 169' in its new position. When the pressure betweenthe two has increased sufficiently, the contacts of the sensitive switch169 will close, thereby again energizing the gear motor 139 which movesthe indexing assembly downward'on ce again. This movement causes thetrip arm 171 in its new position to again recede gradually from thesensitive switch 169 in its new position. When sufficient downwardmovement has occurred to open the contacts of the sensitive switch 169,the gear motor 139 is de-energized and the indexing mechanism retainsthis second newly adjusted position until the contacts of the sensitiveswitch 169 are again closed. This operation repeats. itself as manytimes as is required to keep the feed disk in a position midway betweenthe working surfaces of the abrading wheels.

Control of the quality of output There is provided in the device of thepresent invention.

means to control the thickness of the workpieces produced so that auniform dimension of workpieces is consistently maintained. Thedimensional standards which the workpieces must meet before they areejected from the device as a finished product are predeterminedly setbefore the grinding operation. Workpieces that do not meet. the

standards so set are made to pass through the abrading wheels again bysuitable meansso that a uniform product is regularly obtained. At thetime that suitableimeans are actuated to make each oversize workpiecepassionce again through the abrading wheels, an adjustment of theworking gap between the abrading wheels is simultaneously made tocompensate for wear of the abrading wheels. The mechanism foraccomplishing these functions will now be described.

The sensing means 31, previously mentioned, is shown 1 in Fig. 7 and isresponsive to variations from a predetermined thickness of workpiecesand operates on the workpieces following their exit from between theworking surfaces of the abrading wheels. By way of example, the sensingmeans may be a thickness gauge as shown in the drawings. The sensingmeans may be of any suitable type adapted to close a-pair' of electricalcontacts when the gauge senses that the workpieces are'oversize and toopen the contacts when theworkpieces are within 7 the requiredtolerances. So long as these contacts remain open, that is, when aworkpiece coming off the 9 176 (Figs. 3, 7), previously mentioned, whichruns beneath the workpieces in a substantially continuous circular pathfrom the exit end of the working 'gap to the entrance end of the workinggap, being again broken by the gate 175below the sensing means 31. Theeir cular track 176 beneath the workmeceiving apertures retainstheoversize workpieces within the work-r'eceiving apertures on the feeddisk 17 as they travel from the sensing means 31 back tothe entranceside of the working gap. The track 176 is supported by Z -shaped members178 afiixed to the supporting block 149 for the feed mechanism. Gate 175remains open for workpieces of correct size. If, however, any workpieceis oversize, the electrical contacts of the sensing means are closed.The closing of the electrical contacts of the sensing means 31 completesan electrical circuit which actuates a fluid-actuated cylinder 177, apistonrod 179 of which is in operative relation with the gate 175.Actuation of the fluid-actuated cylinder 177 closes the gate 175 withthe result that the oversized workpiece and succeeding ones to reachthis gate are retained in the feed disk by track 176 to repeat theirpassage between the abrading wheels for additional stock removal. Itwill be apparent that the fluid-actuated cylinder 177 may be replaced bya solenoid or other suitable means.

As has been previously mentioned, the sensing means 31 determineswhether the abrading wheels need vertical adjustment for wheel wear. Theoperation of the sensing means, along with its relation to thepreviously described means for fine adjustment vertically of the gapbetween the abrading wheels will now be described.

Automatic adjustment of the gap between the grinding wheels tocompensate for continual wear of the same during use is brought about bythe sensing means 31 which forms a series circuit with the contacts ofthe previously described switch 107 providing the latter are alsoclosed, which is the case during an adiustably short interval of eachrevolution of the cam 109. For the period of time that this seriescircuit persists, the magnetic clutch 105 is engaged, causing rotationof the screw 91 and thus minutely retracting the wedge 87. Whencorrection is needed, the magnetic clutch 105 is energized to retractthe wedge 87, and each such movement of the wedge 87 permits the upperabrading wheel 27 to make a corresponding downward movement toward thelower disk 29, thus reducing the gap between the abrading wheels. Thereduction of the gap between the abrading wheels reduces the thicknessof the workpieces which may pass therebetween and corrects for theoversize which previously the abrading wheels had produced on theworkpieces. Each such movement of size compensation can occur onlyduring those intervals of simultaneous closing of each of the contactsin the sensing means 31 and the switch 107. The angular speed ofrotation of the cam 109 limits the possible frequency of these comensating movements, whereas the width of the adjustable lobe 111 on thecam 109 determines their duration.- The closing of the contacts of thesensing means 31 determines whether a compensating movement should takeplace, and controls how many successive cycles are required to establishthe desired workpiece thickness.

Setup To facilitate replacing of the abrading wheels and to mount themon their respective shafts, provision is made to unclamp and swing theentire indexing mechanism around the post 147 (Fig. 7) so that the feeddisk 17 occupies the position 17, as shown by the dotted lines inFig. 1. This withdraws the feed disk 17 from the. gap between theabrading wheels. The abrading wheels are rapidly separated a sufiicientdistance by the means previously described to facilitate changeover.After new abrading wheels are installed, the indexing mechanism israised to a height to pass the feed disk 17 over the top surface of thelower abrading disk 29. This may be accomplished by energizing the gearmotor 139, but preferably is done manually by the hand wheel 181 (Fig.3). The indexing mechanism is then swung back to its normal workingposition, as shown in full lines in Fig. 1, and reclamped. The handwheel 93 is cranked to return the wedge 87 to its starting position withthe thicker portions of the wedge between the. rollers 89 and 85, asshown in Fig. 3, as this is the position for new unworn abrading wheels.As the wheels wear, the wedge is automatically retracted laterally untilit occupies the position 87' (Fig. 3) for abrading wheels which haveworn considerably. The sensing means .31 is calibrated for a new setupto close its contacts at the upper tolerance of thickness predeterminedfor the workpieces.

. movement 'to' the succeeding position of rest.

Provision for dressing As hereinbefore mentioned, the need forsupplemental dressing of the abrading wheels is virtually eliminated bythe special features of the present invention. It has been found that itis unnecessary to redress the abrasive disks throughout their wear-life,except in instances of accident or when resetting the machine toaccommodate workpieces of substantially changed physical dimensions.Also, it is preferable to initially dress the working faces of the newabrading wheels to make them fiat and parallel to each other beforeusing them on a new machining operation. However the need may arise,there is provided means for dressing the abrading wheels. To accomplishthis, a dressing unit 183 (Fig. 1), powered by a motor 184, is swungcounter-clockwise from the position shown so as to position its guidebars 185 and 186 parallel to the line passing through the centers of theabrading wheels and a mounting post 187 of dressing unit 183. Theparallel guide bars are connected at one end by a slide block 189 uponwhich are mounted diamond dressing tips 191 above and below the slideblock'189. The diamond dressing tips 191 are adjusted to produce a depthof cut in the upper and lower abrading wheels sufficient to remove anynonuniformity or waviness therein, and then power fed radially across,

the wheel faces. Thereupon, the dressing unit 183 is swung back into itsposition as shown in Fig. 1, which is the inoperative position thereof.

Operation Workpieces are loaded by suitable means (not shown) into theloading chute 21 and the machine is started. When the machine isstarted, fluid pressure enters the cylinder 83 and actuates the pistonrod 81 which moves the rack 79, thereby causing the upper abrading diskto move downward. The rollers 85 prevent further downward travel of theupper abrading wheel when they contact the wedge 87. The fluid cylinder83 is thereupon de-actuated. The gap between the abrading disks ispredicated upon the horizontal position of the wedge 87, the latterbeing disposed with its thicker portion between the rollers 85 and 89for new unworn abrading wheels.

The motor 35 is the source of power for rotary mo tion of the abradingdisks, and the energization of the motor 35 causes the common driveshaft 37 to rotate by means of suitable V-belts and pulleys which alsoprovide for speed adjustability. The upper and lower abrading disks 27and 29 are continuously rotated about a'vertical axis from the powertransmitted to the common drive shaft 37. To provide for a gradualchange of orientation between the working surfaces of the two disks,their relative speeds are made to differ slightly although theirdirection of rotation is the same. The peripheral speeds of the abradingdisks are low as compared to conventional disk grinding and, becauseamoderate speed of abrading movement is employed, a depth of cut isobtained which is sufficient to produce enough grain breakdown on thesurface of the abrading disks to keep the grains sharp withoutsupplemental dressing. The feature of the variable speed drive employedfor rotating the abrading wheels provides for accelerating or retardingthe dressing effect upon the wheels depending upon the physicalproperties of the stock material and the results desired in the finalproduct.

The feed disk 17 has been actuated and is intermittently indexed by theGeneva-type drive previously described. The movement of the feed diskprovides for a controlled time of dwell in one position of rest followedby rapid 7 As each work-receiving aperture 23 of the feed disk 17registers with the loading chute 21, a workpiece is deposited therein.When work-receiving apertures in all of the positions between theabrading disks contain workpieces, the

manual operation of the hand wheel 93 is etfected to withdraw the wedge87 until the upper disk 27 contacts the upper surface of the workpieces.

Preliminary to starting the machine, the thickness gauge 31 isadjustedto respond to the desired thickness of workpiece. Initially eachworkpiece leaving the abrading wheels is oversize and the contacts ofthe gauge 31 are closed. The gate 175 thereby remains closed and theworkpieces will return to the gap between the abrading disks so long asthey remain oversize, being held in their apertures by the track 176.During some portion of each revolution of the cam 199 as determined bythe adjustable lobe 111 thereon, the contacts of the switch 107' close.The simultaneous closure of the contacts of the thickness gauge'31 andthe contacts of the switch 137 forms a series circuit which energizesthe magnetic ciutch 105 causing rotation of the screw 91, thusautomatically retracting the wedge 87. The upper abrading wheel 27 ismoved downward corresponding to each such retraction of the wedge 87 andthe reduction of the working gap thereby elfected begins to compensateby additional stock removal for the oversize of workpieces previouslypro-- duced. This intermittent adjustment of the gap between theabrading disks continues automatically until the desired workpiecethickness is obtained, as indicated by a workpiece passing under thethickness gauge 31 which is within the predetermined tolerance. Whenthis occurs the contacts of the gauge 31 are opened and the fluidcylinder 177 is actuated opening the gate 175. The work piece of thedesired size is allowed to drop out of the feed disk 17 onto theconveyor 33 after being indexed to position over the gate 175. Eachsucceeding workpiece checked and passed by the gauge 31 is conveyed awayto a handling station in a similar manner. It is normal that wheel wearshould occur but since it is substantially equal throughout the annularzones, a series of workpieces will eventually exit from the working gapwhich are oversize from lack of suflicient stock removal. Should thisoccur, the contacts of the gauge 31 will close,

closing the gate 175, thereby preventing the dropping out of theoversize workpieces from the work-receiving apertures 19 and at the sametime intermittently withdrawing the wedge 87 to close the working gapfor additional stock removal. It should be pointed out that not only isthere provided by the means described a sensing means to determinevariation from a predeter-' mined size so that control may be exercisedover the condition causing the variation, but the amount of. controlexercised over the condition is adjustable for work pieces havingdifferent characteristics as by setting the length of the lobe on thecam and the speed of rotation thereof. Furthermore, the total number ofsize com: pensations which occur will be a function of the amount ofvariation of the workpiece from the predetermined size. There is thusprovided an automatic compensation for the working gap which iscompletely reliable in its operation and at the same time is fullysensitive to' all phases of the machining operation sistently uniformoutput.

As the upper abrading disk is automatically adjusted in height relativeto the lower abrading disk to crntrol the quality of output and tocompensate'for wheel wear,

to maintaina con so also is the feed disk automatically adjusted to mainrecedes from the sensitive switch 169 and the gear motor 139 'isde-energized. The feed disk 17 is lowered in proportion to the wearexperienced on the lower abrading disk and the position of the feed diskis always maintained horizontal and midway between the working surfacesof the abrading disks. The control over the adjustment of the indexingassembly, it will be observed, is a function of the amount of wearexperienced by the lower abrading disk.

The novel structure described produces workpieces of a consistentlyuniform size and with a precision parallelism between opposed faces longsought for but heretofore never realized in a flat surface lapper, andmanifestly this is due to the unique operation of the combination ofelements, particular attention being directed. to the manner of feed ofthe workpieces between the abrading disks, the cooperative motion of theabrading wheels and the nature of the wheel wear attendant thereupon.The establishment of annular zones of abrasion by the array ofworkpieces wherein the centerline of those on one side, e. g. the exitside, are disposed at the midpoint of the spaces between those on theother side produces a characteristic wheel wear discovered to occurwhereby the working gap inherently wears so as to maintain itselfparallel as the machining operation proceeds. The annular zones ofabrasion thus established by the novel manner of feed alternate in thetype of work burden assumed and this alternation is thought to accountfor the beneficial self-dressing which continually takes place.

It will be observed that the first annular zone of abrasion isestablished by work done, for example, on a workpiece that is in theinitial position of travel through the working gap while the adjacentzone is established by work done on a workpiece that is in thefurthermost position of travel through the working gap. Similarly, thethird annular zone of abrasion is established by work done, for example,on a workpiece that is in the second position of travel through theworking gap while the adjacent zone is established by work done on aworkpiece that is in the second last position of travel through theworking gap; This alternation in the type of work bur-' den assumed inthe annular zones of abrasion continues in like manner throughout thecross section of the working gap, the effect of which is to self-dressthe working surfaces so that they always tend to remain parallel. Thatthis is true can be demonstrated if it is borne in mind that wear causedby the workpieces on the entrance side of the feed is slightly greaterthan the wear caused by the workpieces on the exit side since the latterare in a more advanced state of completion. Since this is true, theannular zones of abrasion on the entrance side will be slightly greaterin depth due to greater wear than the annular zones on the exit sidebut, since the annular zones on the entrance side alternate with theannular zones on the exit side, the depth of the working gap will remainsubstantially parallel throughout its cross section. A zone havingslightly greater depth due to wear will be adjacent a zone havingslightly lesser depth and the next succeeding adjacent zone will be oneof slightly greater depth followed by one of slightly lesser depth andso on throughout the working gap. The abrading wheels thus tend to wearsubstantially parallel and the need for supplemental dressing has beenfound to be non-existent as a result of this characteristic wheel wear.In actual practice it has been found that, initially, the annular zonesof abrasion on the exit side assume more of the work burden as the zoneson the entrance side wear, until wear on all the zones becomesstabilized and thereafter further wear in each annular zone becomessubstantially equal so that the difference in depth of each alternatezone smooths out to a negligible difference to produce a uniformlyparallel wear between the working surfaces of the abrading disks.

Prominently contributing to this superior type of wheel wearcharacteristic of the machine of the present inven- :asemootion is thefeature of the feed cycle wherein a workpiece is maintained in anannular zone of abrasion for a controlled time of dwell followed by arapid transference to the next succeeding zone for a like period ofdwell. Manifestly, the pronounced effect of these annular zones ofabrasion, established as heretofore described by the amount of work doneon the stock, can be attributed in great measure to this manner ofprogressively indexing them across the working gap.

It will thus be seen from the foregoing description that there has beenprovided a flat surface lapper which produces a consistently uniformproduct throughout its operation, which automatically compensates itselffor the condition of its abrading disks in response to the quality ofits output and which is characterized by uniform wheel wear such thatopposed faces of workpieces exiting from the machine are maintainedparallel throughout the wear life of the abrading disks.

What is claimed is:

1. In a flat surface lapper, a pair of abrading disks having oppositelydisposed working faces lying in substantially parallel planes so as todefine a working gap therebetween, telescoped drive means to rotate saiddisks, means for axially moving one of said telescoped drive meansrelative to the other, means to index a plurality of workpieces throughsaid working gap, sensing means responsive to variations from apredetermined thickness of workpieces leaving said working gap, meansresponsive to said sensing means to axially move one of said drive meansrelative to the other to change the spacing of said disks to adjust thesize of said working gap to compensate for thickness-variations of saidworkpieces from a predetermined thickness, and means to adjust saidindex means to retain it within the space between the abrading disks outof contact therewith.

2. In a flat surface lapper, a pair of abrading disks having oppositelydisposed working faces lying in substantially parallel planes so as todefine a working gap therebetween, telescoped drive means to rotate saiddisks, means for axially moving one of said telescoped drive meansrelative to the other, means to index a plurality of workpieces throughsaid working gap, sensing means responsive to variations from apredetermined thickness of workpieces leaving said working gap, meansresponsive to said sensing means to axially move one of said drive meansrelative to the other to change the spacing of said disks to adjust thesize of said working gap, said last-mentioned means including means tocontrol the frequency and duration of said compensating movements ofsaid one disk, and means to adjust said index means to retain it withinthe space between the abrading disks out of contact therewith.

3. In a flat surface lapper, a pair of abrading disks having oppositelydisposed working faces lying in sub stantially parallel planes so as todefine a working gap therebetween, means to rotate said abrading disks,a feed disk having a plurality of spaced apertures to receive workpiecestherein, means to intermittently index said feed disk through saidworking gap to move said Workpieces toward and away from the center ofsaid working gap, sensing means responsive to variations from apredetermined thickness of workpieces leaving said working gap, 3. firstmeans responsive to said sensing means to move one of said abradingdisks relative to the other of said abrading disks to adjust the size ofsaid working gap, ejecting means associated with said workpieces leavingsaid working gap to eject said workpieces from said feed disk, and asecond means responsive to said sensing means to actuate said ejectingmeans.

4. In a flat surface lapper, a pair of abrading disks having oppositelydisposed working faces lying in substantially parallel planes so as todefine a working gap therebetween, means to rotate said abrading disks,a feed disk having a plurality of spaced apertures to receive workpiecestherein, means to intermittently index said feed disk through saidworking gap to move said work pieces toward and away from the center ofsaid working gap, sensing means responsive to variations from apredetermined thickness of workpieces leaving said'working gap, a firstmeans responsive to said sensing means to move one of said abradingdisks relative to the other of said abrading disks to adjust the size ofsaid working gap, said first meansincluding means to control thefrequency and duration of said compensating movements of said oneabrading disk, ejecting means associated with said workpieces leavingsaid working gap to eject said workpieces from said feed disk, and asecond means responsive to said sensing means to actuate said ejectingmeans.

5. In a flat surface lapper, a pair of abrading disks having oppositelydisposed working faces lying in substantially parallel planes so as todefine a working gap therebetween, means to rotate said abrading disks,a feed disk having a plurality of spaced apertures to receive workpiecestherein, means to intermittently index said feed disk through saidworking gap to move said workpieces toward and away from the center ofsaid working gap, sensing means responsive to a change of dimension ofone of said abrading disks occasioned by wear on the working face ofsaid one abrading disk, and means responsive to said'sensing means tomove said feed disk relative to said one abrading disk to maintainconstant the relative position between said feed disk and the workingface of said one abrading disk.

6. In a fiat surface lapper, a pair of abrading disks having oppositelydisposed working faces lying in substantially parallel planes so as todefine a working gap therebetween, means to rotate said abrading disks,a feed disk having a plurality of spaced apertures to receive workpiecestherein, means to feed said feed disk through said working gap to movesaid workpieces toward and away from the center of said working gap,sensing means responsive to a change of dimension of one of saidabrading disks occasioned by wear on the Working face of said oneabrading disk, and means responsive to said sensing means to move saidfeed disk -relative to said one abrading disk to maintain conhavingoppositely disposed working faces lying in substantially parallel planesso as to define a working gap therebetween, means to rotate saidabrading disks, a feed disk having a plurality of spaced apertures toreceive workpieces therein, means to intermittently index said feed diskthrough said working gap to move said workpieces toward and away fromthe center of said working gap, 21 first sensing means responsive tovariations from a predetermined thickness of workpieces leaving saidworking gap, means responsive to said sensing means to move one of saiddisks relative to-the other of said disks to adjust the size of saidworking gap, a second sensing means responsive to a change of dimensionof one of said abrading disks occasioned by wear on the working face ofsaid one abrading disk, and meansresponsive to said second sensing meansto move said feed disk relative to said one abrading disk to maintainconstant the relative position between said feed disk and the workingface of said one abrading disk.

, 8. In a flat surface lapper, a pair of abrading disks ing means tomove one of said abrading disks relative to the other of said abradingdisks to adjust the size of said working gap, ejecting means associatedwith said workpieces leaving said working gap to eject said workpiecesfrom said feed disk, a second means responsive to said first sensingmeans to actuate said ejecting means, a second sensing means responsiveto a change of dimension of one of said abrading disks occasioned bywear on the working face of said one abrading disk, and means responsiveto said second sensing means to move said feed disk relative to said oneabrading disk to maintain constant the relative position between saidfeed disk and the working face of said one abrading disk.

9 In a flat surface lapper, a pair of abrading disks havlng oppositelydisposed working faces lying in substantially parallel planes so as todefine a working gap therehetween, means to rotate said abrading disks,a feed disk, means to feed said feed disk through said Working gap tomove a plurality of workpieces toward and away from the center of saidworking gap, said feed disk having a plurality of apertures to receivesaid workpieces, said apertures being so spaced on said feed disk thatthe centers of workpieces leaving said working gap occupy the midpointof the spaces between workpieces entering said working gap, sensingmeans responsive to variations from a predetermined thickness ofworkpieces leaving said working gap, a first means responsive to saidsensing means to move one of said abrading disks relative to the otherof said abrading disks to adjustthe size of said working gap, ejectingmeans associated with said workpieces leaving said working gap to ejectsaid workpieces from said feed disk, and a second means responsive tosaid sensing means to actuate said ejecting means.

10. In a flat surface lapper, a pair of abrading disks having oppositelydisposed'working faces'lying in substantially parallel planes so as todefine a working gap therebetween, means to rotate said abrading disks,a

16 abrading disk, ejecting means associated with said workpieces leavingsaid working gap to eject said workpieces from said feed disk, and asecond means responsive to said sensing means to actuate said ejectingmeans.

12. In a flat surface lapper, a pair of abrading disks having oppositelydisposed working faces lying in substantially parallel planes so as todefine a working gap therebetween, means to rotate said abrading disks,a feed disk, means to feed said feed disk through said working gap tomove a plurality of workpieces toward and away from the center of saidworking gap, said feed disk having a plurality of apertures to receivesaid workpieces, said apertures being so spaced on said feed disk thatthe centers of workpieces leaving said working gap occupy the midpointof the spaces between workpieces entering said working gap, sensingmeans responsive to a change of dimension of one of said abrading disksoccasioned by wear on the working face of said one abrading disk, andmeans responsive to said sensing means to move said feed disk relativeto said one abrading disk to maintain constant the relative positionbetween said feed disk and the working face of said one abrading disk.

13. in a flat surface lapper, a pair of abrading disks having oppositelydisposed working faces lying in substantially parallel planes so as todefine a working gap therebetween, means to rotate said abrading disks,a feed disk, means to intermittently index said feed disk through saidworking gap to move a plurality of workpieces toward and away from thecenter of said working gap, said feed disk having a plurality ofapertures to receive said workpieces, said apertures being so spaced onsaid feed disk that the centers of workpieces leaving said working gapoccupy the midpoint of the spaces between feed disk, means to feed saidfeed disk through said working gap to move a plurality of workpiecestoward and away from the center of said working gap, said feed diskhaving a plurality of apertures to receive said workpieces, saidapertures being so spaced on said feed disk that the centers ofworkpieces leaving said working gap occupy the midpoint of the spacesbetween workpiecesentering said working gap, sensing means responsive tovariations from a predetermined thickness of workpieces leaving saidworking gap, a first means responsive to said sensing means to move oneof said abrading disks relative to the other of said abrading disks toadjust the size of said working gap, said first means including means tocontrol the frequency and duration of said compensating movements ofsaid one abrading disk, ejecting means associated with said workpiecesleaving said working gap to eject said workpieces from said feed disk,and a second means responsive to said sensing means to actuate saidejecting means.

11. in a flat surface lapper, a pair of abrading disks having oppositelydisposed working faces lying in substantially parallel planes so as todefine a working gap therebetween, means to rotate said abrading disks,a feed disk, means to intermittently index said feed disk through saidworking gap to move a plurality of workpieces toward and away from thecenter of said working gap, said feed disk having a plurality ofapertures to receive said workpieces, said apertures being so spaced onsaid feed disk that the centers of workpieces leaving said working gapoccupy the midpoint of the spaces between workpieces entering saidworking gap, sensing means responsive to variations from a predeterminedthickness of workpieces leaving said working gap, a first meansresponsive to said sensing means to move one of said abrading disksrelative to the other of said abrading disks to adjust the size of saidworking gap, said first means including means to control the frequencyand duration of said compensating movements of said one workpiecesentering said working gap, sensing means responsive to a change ofdimension of one of said abrading disks occasioned by wear on theworking face of said one abrading disk, and means responsive to saidsensing means to move said feed disk relative to said one abrading diskto maintain constant the relative position between said feed disk andthe working face of said one abrading disk. 7

14. In a fiat surface lapper, a pair of abrading disks having oppositelydisposed working faces lying in substantially parallel planes so as todefine a working gap therebetween, means to rotate said abrading disks,a feed disk, means to intermittently index said feed disk through 1 saidworking gap to move a plurality of workpieces'toward and away from thecenter of said working gap, said feed disk having a plurality ofapertures to receive said workpieces, said apertures being so spaced onsaid feed disk that the centers of workpieces leaving said working gapoccupy the midpoint of the spaces between workpieces entering saidworking gap, a first sensing means responsive to variations from apredetermined thickness of work pieces leaving said working gap, meansresponsive to sald first sensing means to move one of said abradingdISkS relative to the other of said abrading disks to adjust the size ofsaid working gap, a second sensing means responsive to a change ofdimension of one of said abrading disks occasioned by wear on theworking face of said one abrading disk, and means responsive to saidsecond sensing means to move said feed disk relative to saidone abradingdisk to maintain constant the relative position between said feed diskand the working face of said one abrading disk,

15. In a fiat surface lapper, a pair of abrading disks having oppositelydisposed working faces lying in substantially parallel planes so as todefine a working gap therebetween, means to rotate said abrading disks,a feed disk, means to feed said feed disk through said working gap'tomove a plurality of workpieces toward and away from the center of saidworking gap, said feed disk having a plurality'of apertures to receivesaid workpieces, said apertures being so spaced on said feed disk thatthe centers, of workpieces leaving said working gap occupy the midpointof the spaces between workpieces entering said working gap, a firstsensing means responsive to variations from a predetermined thickness ofworkpieces leaving said working gap, means responsive to said firstsensing means to move one of said abrading disks relative to the otherof said abrading disks to adjust the size of said working gap, a secondsensing means responsive to a change of dimension of one of saidabrading disks occasioned by wear on the working face of said oneabrading disk, and means responsive to said second sensing means to movesaid feed disk relative to said one abrading disk to maintain constantthe relative position between said feed disk and the working face ofsaid one abrading disk.

16. In a flat surface lapper, a pair of abrading disks having oppositelydisposed working faces lying in substantially parallel planes so as todefine a working gap therebetween, means to rotate said abrading disks,a feed disk, means to intermittently index said feed disk through saidworking gap to move a plurality of workpieces toward and away from thecenter of said working gap, said feed disk having a plurality ofapertures to receive said workpieces, said apertures being so spaced onsaid feed disk that the centers of workpieces leaving said working gapoccupy the midpoint of the spaces between workpieces entering saidworking gap, a first sensing means responsive to variations from apredetermined thickness of workpieces leaving said working gap, a firstmeans responsive to said first sensing means to move one of saidabrading disks relative to the other of said abrading disks to adjustthe size of said working gap, ejecting means associated with saidworkpieces leaving said working gap to eject said workpieces from saidfeed disk, a second means responsive to said first sensing means toactuate said ejecting means, a second sensing means responsive to achange of dimension of one of said abrading disks occasioned by wear onthe working face of said one abrading disk, and means responsive to saidsecond sensing means to move said feed disk relative to said oneabrading disk to maintain constant the relative position between saidfeed disk and the working face of said one abrading disk.

17. In a flat surface lapper, a pair of abrading disks having oppositelydisposed working faces lying in substantially parallel planes so as todefine a working gap therebetween, means to rotate said abrading disks,a feed disk, means to feed said feed disk through said working gap tomove a plurality of workpieces toward and away from the center of saidworking gap, said feed disk having a plurality of apertures to receivesaid workpieces, said apertures being so spaced on said feed disk thatthe centers of workpieces leaving said working gap occupy the midpointof the spaces between workpieces entering said working gap, a firstsensing means responsive to variations from a predetermined thickness ofworkpieces leaving said working gap, a first means responsive to saidfirst sensing means to move one of said abrading disks relative to theother of said abrading disks to adjust the size of said working gap,ejecting means associated with said workpieces leaving said working gapto eject said workpieces from said feed disk, a second means responsiveto said first sensing means to actuate said ejecting means, a secondsensing means responsive to a change of dimension of one of saidabrading disks occasioned by wear on the working face of said oneabrading disk, and means responsive to said second sensing means to movesaid feed disk relative to said one abrading disk to maintain constantthe relative position between said feed disk and the working face ofsaid one abrading disk.

18. In a flat surface lapping device, a pair of abrading disks havingoppositely disposed abrading faces lying in substantially parallelplanes and spaced apart to provide a workpiece receiving gaptherebetween, drive means for said disks, a third disk having aperturestherethrough near the peripheral edge for carrying workpieces throughsaid gap to have the opposite ends thereof machined by said abradingfaces, sensing means responsive to an increase in thickness of the spacebetween the dressed ends of the workpiece, means responsive to saidsensing means for adjusting one of said disks for decreasing the gapbetween the abrasive disks, and means for adjusting another of saiddisks to have the said third disk disposed substantially midway in saidgap out of contact with said working faces.

References Cited in the file of this patent UNITED STATES PATENTS1,198,772 Roach Sept. 19, 1916 1,371,854 Buck Mar. 15, 1921 1,926,974Einstein Sept. 12, 1933 2,122,942 Hutchinson July 5, 1938 2,148,744 HallFeb. 28, 1939 2,580,542 Heath Jan. 1, 1952 FOREIGN PATENTS 417,400 GreatBritain Oct. 4, 1934 661,214 Great Britain Nov. 21, 1951 718,087 GreatBritain Nov. 10, 1954

